In the last few years, one of the most prolific iOS bug hunters has been working for Project Zero, Google’s elite hacker team dedicated to finding zero-days in other companies’ products, quashing bug after bug. His name is Ian Beer and some consider him the best iOS hacker out there.

On Wednesday, after a talk at the Black Hat security conference in Las Vegas, Beer tweeted a message to Apple’s CEO Tim Cook, challenging him to pay for each bug he has reported since 2016, and asking him to donate $2.45 million to to human rights group Amnesty International.

An Apple spokesperson declined to comment, and Beer could not be reached for comment.

“I'd love to get a chance to sit down with you and discuss how together we can make iOS even more secure for all our users. Cheers, Ian Beer,” he tweeted.